Monitor for high dose rate electron therapy, system and method

ABSTRACT

A method of monitoring a radiation dose includes impinging an electrode with radiation and measuring a current through the electrode. Emission of secondary electrons emitted from the electrode provides a majority of the current.

RELATED APPLICATION(S)

This Application is a Continuation of co-pending, commonly owned U.S.patent application Ser. No. 17/353,538 (attorney docket 2021P60018 US),entitled “Monitor for High Dose Rate Electron Therapy, System andMethod,” filed Jun. 21, 2021, which is hereby incorporated herein byreference in its entirety.

FIELD OF INVENTION

Embodiments of the present invention relate to the field of medicaldevices. More specifically, embodiments of the present invention relateto systems and methods for monitoring high dose rate electron beamtherapy.

BACKGROUND

External beam radiation therapy may be used in the treatment of variouscancers and non-malignant conditions. Generally, ionizing radiation,including, for example, photons, e.g., X-rays, gamma rays, and chargedparticles, e.g., protons and electrons, is directed at an area ofinterest. In many cases, such ionizing radiation is generated by alinear accelerator or a cyclotron.

It is critical to accurately measure the dose of such radiation duringtreatment. For example, radiotherapy is typically very precisely plannedbased on numerous factors, including, for example, tumor type, tumorlocation, and stage, as well as the general health of the patient. Ingeneral, too much radiation may harm a patient, and too little radiationmay not achieve a desired therapeutic effect.

Conventionally, an ionization chamber is utilized to measure radiationdosage and/or dose rate based on radiation-induced ionization in a gas.A sample gas is enclosed in an ionization chamber between twoelectrodes. The radiation “beam” is directed through the ionizationchamber prior to impacting a patient, causing some of the sample gas tobe ionized. The ionization typically creates a negatively chargedelectron and a positive ion. A voltage applied to the electrodes, forexample 500 volts, collects the electrons on the positive electrode andcollects positive ions on the negative electrode. A current collected bythese electrodes is generally proportional to the radiation dose rate,and may be measured to create a dose monitor. As long as the radiationionizes only a small fraction of the gas, the current will be linearwith respect to dose rate.

FLASH radiotherapy is an emerging radiotherapy regime that appears toreduce radiation-induced toxicities while maintaining a tumor responsesimilar to that of more conventional radiotherapy regimes. FLASHradiotherapy may be characterized as delivering a high radiation rate,e.g., greater than about 40 grays (Gy) per second, that allows for atotal radiotherapy treatment dose, or large fractions of a totalradiation dose, to be delivered in parts of a second, compared toseveral minutes for conventional radiotherapy. For example, aconventional radiotherapy treatment may include a total dose of 12-25grays (Gy) delivered at a rate of up to 0.4 Gy/s, requiring minutes oftreatment time. In contrast, FLASH radiotherapy may deliver a similartotal dose at a rate of 40 Gy/s, requiring a fraction of a second oftreatment time.

However, when radiation dose rates are very high, as is the case withFLASH radiotherapy, conventional dosage monitoring devices become lessaccurate than desired. Due to the high radiation intensity, a great manyelectron/ion pairs are created such that electrons and ions make up asignificant fraction of the sample gas, and ions/electrons fromdifferent tracks encounter each other on their way to the collectingelectrode(s). As a result, recombination between electrons and ionsoccurs at a high rate that varies with the dose rate, and the measuredcurrent no longer corresponds linearly to the radiation dose rate. Thus,conventional dosage monitoring devices are generally not accurate enoughfor use with FLASH radiotherapy.

SUMMARY OF THE INVENTION

Therefore, what is needed are systems and methods for monitoring highdose rate electron beam therapy. What is additionally needed are systemsand methods for monitoring high dose rate electron beam therapy thataccurately measure radiotherapy doses of FLASH radiotherapy. Further,there is a need for systems and methods for monitoring high dose rateelectron beam therapy that accurately measure radiotherapy doses of bothconventional radiotherapy and FLASH radiotherapy. There is a furtherneed for systems and methods for monitoring high dose rate electron beamtherapy that are compatible and complementary with existing systems andmethods of administering radiotherapy.

In accordance with an embodiment of the present invention, aradiotherapy dose rate monitor system includes an electrode configuredto be impinged by radiotherapy radiation, and a current measurementcircuit configured to measure a current through the electrode. Anemission of secondary electrons emitted from the electrode provides amajority of current through the electrode.

According to another embodiment, a radiotherapy dose rate monitor systemincludes an electrode configured to be impinged by radiotherapyradiation, a resistor coupled to the electrode and to ground, and avoltage measurement device configured to measure a voltage through theresistor corresponding to a radiotherapy dose rate. The dose ratemonitor system is operable in a first mode or a second mode. The firstmode corresponds to a dose rate characteristic of FLASH radiotherapy andthe second mode corresponds to a dose rate of less than 40 Gy/s.

According to another embodiment, a radiotherapy dose rate monitor systemincludes a first electrode, a first resistor configured to couple thefirst electrode to ground, and a first voltage sensor configured tomeasure a first voltage across the first resistor. The first voltage isindicative of a first radiation dose passing through the firstelectrode. The radiotherapy dose rate monitor system is configured tomeasure radiotherapy dose rates of greater than or equal to 40 Gy/s toan accuracy of better than 98% during patient treatment.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthis specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention. Unless otherwise noted, the drawings may not be drawn toscale.

FIG. 1 illustrates a block diagram of an exemplary radiation treatmentsystem that may serve as a platform for embodiments in accordance withthe present invention.

FIG. 2 illustrates a schematic of an exemplary beam path within anexemplary radiation treatment system, in accordance with embodiments ofthe present invention.

FIGS. 3A and 3B illustrate an exemplary scattering/monitoring foil, inaccordance with embodiments of the present invention.

FIG. 4 illustrates a schematic diagram of an exemplary single electrodeas part of a scattering/monitor foil, in accordance with embodiments ofthe present invention.

FIG. 5 is a simplified flowchart of an exemplary method of measuring aradiotherapy dose rate, in accordance with embodiments of the presentinvention.

FIG. 6 illustrates a block diagram of an exemplary electronic system,which may be used as a platform to implement and/or as a control systemfor embodiments of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction withthese embodiments, it is understood that they are not intended to limitthe invention to these embodiments. On the contrary, the invention isintended to cover alternatives, modifications and equivalents, which maybe included within the spirit and scope of the invention as defined bythe appended claims Furthermore, in the following detailed descriptionof the invention, numerous specific details are set forth in order toprovide a thorough understanding of the invention. However, it will berecognized by one of ordinary skill in the art that the invention may bepracticed without these specific details. In other instances, well knownmethods, procedures, components, and circuits have not been described indetail as not to unnecessarily obscure aspects of the invention.

Some portions of the detailed descriptions which follow (e.g., method500) are presented in terms of procedures, steps, logic blocks,processing, and other symbolic representations of operations on databits that may be performed on computer memory. These descriptions andrepresentations are the means used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. A procedure, computer executed step, logicblock, process, etc., is here, and generally, conceived to be aself-consistent sequence of steps or instructions leading to a desiredresult. The steps are those requiring physical manipulations of physicalquantities. Usually, though not necessarily, these quantities take theform of electrical or magnetic signals capable of being stored,transferred, combined, compared, and otherwise manipulated in a computersystem. It has proven convenient at times, principally for reasons ofcommon usage, to refer to these signals as bits, values, elements,symbols, characters, terms, numbers, data, or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the followingdiscussions, it is appreciated that throughout the present invention,discussions utilizing terms such as “applying” or “controlling” or“generating” or “testing” or “heating” or “bringing” or “capturing” or“storing” or “reading” or “analyzing” or “resolving” or “accepting” or“selecting” or “determining” or “displaying” or “presenting” or“computing” or “sending” or “receiving” or “reducing” or “detecting” or“setting” or “accessing” or “placing” or “forming” or “mounting” or“removing” or “ceasing” or “stopping” or “coating” or “processing” or“performing” or “adjusting” or “creating” or “executing” or “continuing”or “indexing” or “translating” or “calculating” or “measuring” or“gathering” or “running” or the like, refer to the action and processesof, or under the control of, a computer system, or similar electroniccomputing device, that manipulates and transforms data represented asphysical (electronic) quantities within the computer system's registersand memories into other data similarly represented as physicalquantities within the computer system memories or registers or othersuch information storage, transmission or display devices.

The meaning of “non-transitory computer-readable medium” should beconstrued to exclude only those types of transitory computer-readablemedia which were found to fall outside the scope of patentable subjectmatter under 35 U.S.C. § 101 in In re Nuijten, 500 F.3d 1346, 1356-57(Fed. Cir. 2007). The use of this term is to be understood to removeonly propagating transitory signals per se from the claim scope and doesnot relinquish rights to all standard computer-readable media that arenot only propagating transitory signals per se.

In the following disclosure, exemplary embodiments in accordance withthe present invention are illustrated in terms of a linear acceleratorand radiotherapy particles, e.g., electrons. However, it will beappreciated by those skilled in the art that the same or similarprinciples apply to other systems, including, for example, cyclotrons,and other types of ionizing radiation, including, for example, photons,e.g., X-rays, protons, and/or other particles. All such systems are wellsuited to, and are within the scope of embodiments in accordance withthe present invention.

In the following descriptions, various elements and/or features ofembodiments in accordance with the present invention are presented inisolation so as to better illustrate such features and as not tounnecessarily obscure aspects of the invention. It is to be appreciated,however, that such features, e.g., as disclosed with respect to a firstdrawing, may be combined with other features disclosed in other drawingsin a variety of combinations. All such embodiments are anticipated andconsidered, and may represent embodiments in accordance with the presentinvention.

Monitor for High Dose Rate Electron Therapy, System and Method

FIG. 1 illustrates a block diagram of an exemplary radiation treatmentsystem 100 that may serve as a platform for embodiments in accordancewith the present invention. Radiation treatment system 100 may besimilar to a TrueBeam® radiotherapy system, commercially available fromVarian Medical Systems, Palo Alto, Calif.

Stand 10 supports a rotatable gantry 20 with a treatment head 30. Thetreatment head 30 may extend into the gantry 20. In proximity to stand10 there is arranged a control unit (not shown) which includes controlcircuitry for controlling the different modes of operation of the system100.

Radiation treatment system 100 comprises a linear accelerator 40, forexample, within gantry 20, utilized to create a radiation beam.Typically, radiation treatment system 100 is capable of generatingeither an electron (particle) beam or an x-ray (photon) beam for use inthe radiotherapy treatment of patients on a treatment couch 35. Otherradiation treatment systems are capable of generating heavy ionparticles such as protons. For purposes of the following disclosure,only electron irradiation will be discussed.

A high voltage source is provided within the stand and/or in the gantryto supply voltage to an electron gun (not shown) positioned on anaccelerator guide located in the gantry 20. Electrons are emitted fromthe electron gun into the accelerator 40 where they are accelerated. Asource supplies radio frequency (microwave) power for the generation ofan electric field within the waveguide. The electrons emitted from theelectron gun are accelerated in the waveguide by the electric field, andexit the waveguide as a high-energy electron beam 45, for example, atmegavoltage energies. The electron beam 45 then strikes a suitable metalreflector 50, redirecting high energy electrons 55 in the direction of apatient P. In some embodiments, the electrons 55 may be redirectedtoward the patient by a system of one or more bend magnets.

As illustrated in FIG. 1 , a patient P is shown lying on the treatmentcouch 35. High energy electrons as described above are emitted from thetreatment head 30 in a divergent beam 104. Typically, a patient plane116, is positioned, for example, about one meter from the electronsource, and the rotational axis of the gantry 20 is located on the plane116, such that the distance between the target and the isocenter 178remains constant when the gantry 20 is rotated. It is appreciated thatfor electron FLASH therapy, the patient plane 116 may be less than onemeter from the electron source. The isocenter 178 is at the intersectionbetween the patient plane 116 and the central axis of beam 122. Atreatment volume to be irradiated may be located about the isocenter178. It is appreciated that some treatment plans may utilize a primarytarget that is off of the central beam axis, and such arrangements arewithin the scope of embodiments in accordance with the presentinvention.

FIG. 2 illustrates a schematic of an exemplary beam path 200 withinexemplary radiation treatment system 100, in accordance with embodimentsof the present invention. It is appreciated that the illustratedcomponents of beam path 200 are exemplary, and all may not be requiredin some embodiments. Additional components, e.g., a flattening filter(not shown), may also be included in accordance with embodiments of thepresent invention. A radiation beam 204 passes through primarycollimator 210, X and Y jaws 230, and multi-leaf collimator 240. Theprimary collimator may comprise a plurality of selectable collimatorsand/or filters, in some embodiments. The primary collimator, X and Yjaws 230, and the leaves of the multi-leaf collimator (MLC) 240typically comprise an electron blocking material, and are positioned inthe head 30 (FIG. 1 ) to define the width of the electron beam at thepatient plane. Typically, the X and Y jaws 230 are moveable and, whenfully open, define a maximum beam width at the patient plane 116 (FIG. 1). The MLC 330 is positioned at the exit of the head 30, to furthershape the electron beam. Exemplary MLCs may use up to 120 individuallycontrollable leaves, for example, thin slices of tungsten, which may bemoved into or out of the electron beam under the control of systemsoftware.

In accordance with embodiments of the present invention, ascattering/monitor foil 220 is placed within radiation beam 204.Generally, scattering/monitor foil 220 may be placed between a primarycollimator 210 and X and Y jaws 230, although that is not required.Scattering/monitor foil 220 may be utilized to spread, or “scatter,” aradiotherapy beam, in some embodiments. For example, a very narrow or“tight” radiation beam is spread out to form a broader radiation field.Scattering/monitor foil 220 is further utilized to measure the radiationdose delivered by radiation beam 204, in accordance with embodiments ofthe present invention.

In some embodiments, a monitor foil may be separate from a scatteringfoil. For example, a radiotherapy system includes a conventionalscattering foil and a separate, novel monitoring foil. Embodiments inaccordance with the present invention are well suited to a separatemonitor foil and/or a combined scattering/monitor foil.

FIGS. 3A and 3B illustrate an exemplary scattering/monitor foil 220, inaccordance with embodiments of the present invention. Scattering/monitorfoil 220 may be utilized, for example, in radiation treatment system100, to measure a radiation dose and/or dose rate, for example.Scattering/monitor foil 220 typically provides closed loop feedback toportions of radiation treatment system 100 (FIG. 1 ) to control theintensity of beam 204. Scattering/monitor foil 220 typically alsoprovides a record of a treatment dose. Scattering/monitor foil 220 mayfurther function as part of an emergency shut off capability if a safeand/or a prescribed level of radiation is not achieved, e.g., too muchor too little radiation. At least a portion of scattering/monitor foil220 is positioned within radiation beam 204, as illustrated in FIG. 2 .FIG. 3A illustrates a side-sectional view of an exemplaryscattering/monitor foil 220, in accordance with embodiments of thepresent invention.

Scattering/monitor foil 220 may comprise a thin conductive foil, forexample comprising aluminum 0.0007 inches (17.78 μm) thick. Otherthicknesses, e.g., 0.0008 inches to 0.009 inches (20-230 μm), andmaterials, e.g., brass, copper, and/or gold, may be suitable. Forexample, thicker foils may be suited to higher electron energies.Conventionally, a scattering foil is electrically floating or grounded.In accordance with embodiments of the present invention,scattering/monitor foil 220 may be coupled to a current measuringcircuit 305. As will be described further with respect to FIG. 4 below,current measuring circuit 305 is configured to measure a current due tothe emission of secondary electrons from scattering/monitor foil 220 dueto an impinging radiation beam, e.g., radiation beam 204. Any suitablecurrent measuring circuit may be used, including, for example,electrical and/or magnetic circuits, and passive and/or active circuits.

In accordance with embodiments of the present invention, a resistor maybe utilized to measure such a current. In some embodiments,scattering/monitor foil 220 is coupled to a relative ground, e.g., anearth ground, a chassis ground, a local ground, a current return path,and/or an electron source, via a monitoring resistor 310. An exemplaryresistance value for monitoring resistor 310 is 50 ohms, in someembodiments. Other resistance values may be suitable. For example,different resistance values may be suited to different dosage rates. Insome embodiments, the monitoring resistor 310 may be utilized to couplethermal energy away from the monitor foil. It is appreciated thatmonitor resistor 310 is an example of a current measurement circuit 305,and that generally only one type of current measurement circuit would beutilized per electrode.

Scattering/monitor foil 220 may comprise multiple electrodes in someembodiments. Such multiple electrodes may be mounted to a separatesubstrates and/or formed by an electrical interruption in asubstantially planar and/or foil structure. FIG. 3B illustrates a planview of an exemplary arrangement of a four-electrode scattering/monitorfoil 220, in accordance with embodiments of the present invention.Embodiments in accordance with the present invention are well suited tomore or fewer electrodes, as well as to different shape(s) andorientations of electrodes. In embodiments comprising multipleelectrodes, each electrode should be electrically isolated from anyother electrodes, and each electrode should be separately grounded via aseparate instance of a monitoring resistor 310 (not shown in FIG. 3B).It is appreciated that all electrodes are not required to be the sameshape, in some embodiments. It is further appreciated that all instancesof a monitoring resistor 310 are not required to comprise the sameresistance value and/or be of the same construction, in someembodiments. In some embodiments, monitoring resistor 310 is locatedoutside of radiotherapy beam 204.

Exemplary scattering/monitoring foil 220 comprises four electrodes:inner electrode 320, inner electrode 325, outer electrode 330, and outerelectrode 335. The inner electrodes, 320 and 325, may be configured tobe completely within the incident radiation beam 204. The innerelectrodes, 320 and 325, may be configured to measure a total dose rateof the incident radiation beam 204. Any dose rate difference betweeninner electrodes 320 and 325 may reveal a beam 204 angle symmetry error.

The outer electrodes, 330 and 335, may be configured to be partiallywithin the beam 204, e.g., on an edge of beam 204. Any dose ratedifference between outer electrodes 330 and 335 may reveal a beam 204position symmetry error.

FIG. 4 illustrates a schematic diagram 400 of an exemplary singleelectrode as part of a scattering/monitor foil 220, in accordance withembodiments of the present invention. An electrode of scattering/monitorfoil 220 is coupled to relative ground through current measuring circuit305, embodied as monitor resistor 310 in a monitor resistor embodiment.Any additional electrodes (not shown) would be coupled to relativeground through current measuring circuits and/or parallel resistors. Insome embodiments, during operation, radiation-therapy beam 204 passesthrough scattering/monitor foil 220, displacing secondary electrons 410.The secondary electrons 410 may render a positive charge onscattering/monitor foil 220, which may cause a current to flow throughmonitor resistor 310, resulting in a voltage difference 420 acrossmonitor resistor 310. Electronic circuitry (not shown) may detectvoltage difference 420, using voltage difference 420 as an indication ofthe dosage rate of radiotherapy beam 204.

In contrast to conventional radiotherapy dose rate monitors that mayutilize a circuit comprising multiple electrodes, embodiments inaccordance with the present invention utilize a circuit having a singleelectrode. In addition, embodiments in accordance with the presentinvention do not require a voltage externally applied to the electrode.

It is anticipated that some radiotherapy dosage regimes may cause anegative charge to accumulate on an electrode of a scattering/monitorfoil 220. Such a circumstance would reverse the current and voltagedifference 420 described previously, and is considered within the scopeof embodiments in accordance with the present invention.

Radiotherapy is typically delivered in very short pulses. For example, aconventional radiotherapy system may deliver 360 pulses per second, witheach pulse having a duration of about 4 μs. Each pulse may provide adose of about 1 mGy, for example. Such an exemplary protocol deliversabout 0.4 Gy/s on a time average basis. FLASH radiotherapy may becharacterized as delivering a radiation dose greater than or equal to 40grays (Gy) per second, on a time average basis. Embodiments inaccordance with the present invention enable accurate dosage anddosage-rate measurements of FLASH radiotherapy, thereby enablingtherapeutic use of FLASH radiotherapy.

At high radiation intensities, e.g., equal to or greater than about 2mGy per 4 μs pulse, conventional dosage monitoring devices, e.g., ionchambers, are generally not accurate enough for use with high intensityand/or FLASH radiotherapy. For example, such conventional dosagemonitoring devices are generally not able to achieve greater than orequal to 98% accuracy in reporting high intensity and/or FLASHradiotherapy dose rates. Embodiments in accordance with the presentinvention are able to provide greater than or equal to 98% accuracy inreporting high intensity and/or FLASH radiotherapy dose rates, e.g.,greater than or equal to 40 Gy/s. Accuracy may be determined incomparison to other well-known dosimeter devices that are typically notused during treatment, including, for example, external probes and/orfilm dosimeters.

Referring once again to FIG. 1 , many conventional radiotherapy systemsare designed to rotate around the isocenter 178 of patient P, in orderto distribute a radiation dose over all of the surrounding tissue whiledelivering an entire dose to the target tissue. One potential benefit ofFLASH radiotherapy is that it appears to reduce radiation-induced damageto surrounding tissues while maintaining a tumor response equivalent tothat of more conventional radiotherapy regimes. This benefit of FLASHradiotherapy may reduce the benefit(s) of such rotation. Embodiments inaccordance with the present invention provide systems and methods ofaccurately measuring dose and/or dose rates of FLASH radiotherapy.Accordingly, embodiments in accordance with the present invention mayfacilitate non-rotational FLASH radiotherapy, beneficially reducing thecost, complexity, and room-size requirements of such radiotherapysystems.

Conventional radiotherapy dose rate measurement systems, e.g., based onion chambers, may produce an electrical current based on ionization of agas and/or emission of secondary electrons, e.g., from chamberelectrodes. A portion of current from either source may vary based onthe design of ion chamber and/or the radiotherapy intensity. Incontrast, in accordance with embodiments of the present invention, amajority of current corresponding to a radiotherapy dose rate isproduced by secondary electrons emitted from the electrode. Such asingle current producing mechanism may be advantageous for calibrationof dose rate measurements across a wide range of radiotherapy dosagerates.

As previously presented, when radiotherapy dose rates are very high, asis the case with FLASH radiotherapy, conventional dosage monitoringdevices become less accurate than desired. Embodiments in accordancewith the present invention enable accurate dosage monitoring for highradiation dose rates. In addition, embodiments in accordance with thepresent invention are capable of providing accurate dosage monitoringfor lower and/or conventional radiation dose rates, e.g., dose rates atless that FLASH radiotherapy rates. Accordingly, embodiments inaccordance with the present invention may be operated in at least twomodes, for example, a first mode that corresponds to a dose ratecharacteristic of FLASH radiotherapy, and a second mode that correspondsto a dose rate of less than 40 Gy/s. In some embodiments, calibration ofcurrent measurement(s) may vary among such mode(s), although that is notrequired.

FIG. 5 is a simplified flowchart of an exemplary method 500 of measuringa radiotherapy dose rate, in accordance with embodiments of the presentinvention. Method 500 may be performed wholly or partially with acomputer system, e.g., computer system 600 of FIG. 6 .

In 510, an electrode, e.g., of a scattering/measuring foil 220 (FIG. 4), is coupled to a current measuring circuit, e.g., current measuringcircuit 305 (FIG. 3A). The current measuring circuit may comprisecoupling the scattering/measuring foil 220 to a relative ground via aresistor, e.g., monitor resistor 310 (FIG. 3A). In 520, the electrode isexposed to radiotherapy radiation. The radiotherapy radiation may be atdose rate intensities corresponding to FLASH radiotherapy.

In 530, a current through the electrode is measured. For example, avoltage across the resistor due to secondary electron emission from theelectrode is measured to indicate a dose rate of the radiotherapyradiation. In optional 540, the indication of dose rate is used asfeedback to control a dose rate of FLASH radiotherapy.

FIG. 6 illustrates a block diagram of an exemplary electronic system600, which may be used as a platform to implement and/or as a controlsystem for embodiments of the present invention. Electronic system 600may be a “server” computer system, in some embodiments. Electronicsystem 600 includes an address/data bus 650 for communicatinginformation, a central processor complex 605 functionally coupled withthe bus for processing information and instructions. Bus 650 maycomprise, for example, a Peripheral Component Interconnect Express(PCIe) computer expansion bus, industry standard architecture (ISA),extended ISA (EISA), MicroChannel, Multibus, IEEE 796, IEEE 1196, IEEE1496, PCI, Computer Automated Measurement and Control (CAMAC), MBus,Runway bus, Compute Express Link (CXL), and the like.

Central processor complex 605 may comprise a single processor ormultiple processors, e.g., a multi-core processor, or multiple separateprocessors, in some embodiments. Central processor complex 605 maycomprise various types of well-known processors in any combination,including, for example, digital signal processors (DSP), graphicsprocessors (GPU), complex instruction set (CISC) processors, reducedinstruction set (RISC) processors, and/or very long word instruction set(VLIW) processors. In some embodiments, exemplary central processorcomplex 605 may comprise a finite state machine, for example, realizedin one or more field programmable gate array(s) (FPGA), which mayoperate in conjunction with and/or replace other types of processors tocontrol embodiments in accordance with the present invention.

Electronic system 600 may also include a volatile memory 615 (e.g.,random access memory RAM) coupled with the bus 650 for storinginformation and instructions for the central processor complex 605, anda non-volatile memory 610 (e.g., read only memory ROM) coupled with thebus 650 for storing static information and instructions for theprocessor complex 605. Electronic system 600 also optionally includes achangeable, non-volatile memory 620 (e.g., NOR flash) for storinginformation and instructions for the central processor complex 605 whichcan be updated after the manufacture of system 600. In some embodiments,only one of ROM 610 or Flash 620 may be present.

Also included in electronic system 600 of FIG. 6 is an optional inputdevice 630. Device 630 can communicate information and commandselections to the central processor 600. Input device 630 may be anysuitable device for communicating information and/or commands to theelectronic system 600. For example, input device 630 may take the formof a keyboard, buttons, a joystick, a track ball, an audio transducer,e.g., a microphone, a touch sensitive digitizer panel, eyeball scanner,and/or the like.

Electronic system 600 may comprise a display unit 625. Display unit 625may comprise a liquid crystal display (LCD) device, cathode ray tube(CRT), field emission device (FED, also called flat panel CRT), lightemitting diode (LED), plasma display device, electro-luminescentdisplay, electronic paper, electronic ink (e-ink) or other displaydevice suitable for creating graphic images and/or alphanumericcharacters recognizable to the user. Display unit 625 may have anassociated lighting device, in some embodiments.

Electronic system 600 also optionally includes an expansion interface635 coupled with the bus 650. Expansion interface 635 can implement manywell known standard expansion interfaces, including without limitationthe Secure Digital Card interface, universal serial bus (USB) interface,Compact Flash, Personal Computer (PC) Card interface, CardBus,Peripheral Component Interconnect (PCI) interface, Peripheral ComponentInterconnect Express (PCI Express), mini-PCI interface, IEEE 1394, SmallComputer System Interface (SCSI), Personal Computer Memory CardInternational Association (PCMCIA) interface, Industry StandardArchitecture (ISA) interface, RS-232 interface, and/or the like. In someembodiments of the present invention, expansion interface 635 maycomprise signals substantially compliant with the signals of bus 650.

A wide variety of well-known devices may be attached to electronicsystem 600 via the bus 650 and/or expansion interface 635. Examples ofsuch devices include without limitation rotating magnetic memorydevices, flash memory devices, digital cameras, wireless communicationmodules, digital audio players, and Global Positioning System (GPS)devices.

System 600 also optionally includes a communication port 640.Communication port 640 may be implemented as part of expansion interface635. When implemented as a separate interface, communication port 640may typically be used to exchange information with other devices viacommunication-oriented data transfer protocols. Examples ofcommunication ports include without limitation RS-232 ports, universalasynchronous receiver transmitters (UARTs), USB ports, infrared lighttransceivers, ethernet ports, IEEE 1394, and synchronous ports.

System 600 optionally includes a network interface 660, which mayimplement a wired or wireless network interface. Electronic system 600may comprise additional software and/or hardware features (not shown) insome embodiments.

Various modules of system 600 may access computer readable media, andthe term is known or understood to include removable media, for example,Secure Digital (“SD”) cards, CD and/or DVD ROMs, diskettes and the like,as well as non-removable or internal media, for example, hard drives,solid state drive s (SSD), RAM, ROM, flash, and the like.

Embodiments in accordance with the present invention provide systems andmethods for monitoring high dose rate electron beam therapy. Inaddition, embodiments in accordance with the present invention providesystems and methods for monitoring high dose rate electron beam therapythat accurately measure radiotherapy doses of FLASH radiotherapy.Further, embodiments in accordance with the present invention providesystems and methods for monitoring high dose rate electron beam therapythat accurately measure radiotherapy doses of both conventionalradiotherapy and FLASH radiotherapy. Further, embodiments in accordancewith the present invention provide systems and methods for monitoringhigh dose rate electron beam therapy that are compatible andcomplementary with existing systems and methods of administeringradiotherapy.

Although the invention has been shown and described with respect to acertain exemplary embodiment or embodiments, equivalent alterations andmodifications will occur to others skilled in the art upon the readingand understanding of this specification and the annexed drawings. Inparticular regard to the various functions performed by the abovedescribed components (assemblies, devices, etc.) the terms (including areference to a “means”) used to describe such components are intended tocorrespond, unless otherwise indicated, to any component which performsthe specified function of the described component (e.g., that isfunctionally equivalent), even though not structurally equivalent to thedisclosed structure which performs the function in the hereinillustrated exemplary embodiments of the invention. In addition, while aparticular feature of the invention may have been disclosed with respectto only one of several embodiments, such feature may be combined withone or more features of the other embodiments as may be desired andadvantageous for any given or particular application.

Various embodiments of the invention are thus described. While thepresent invention has been described in particular embodiments, itshould be appreciated that the invention should not be construed aslimited by such embodiments, but rather construed according to the belowclaims.

We claim:
 1. A method of monitoring a radiation dose, the methodcomprising: impinging an electrode with radiation; measuring a currentthrough said electrode, and wherein emission of secondary electronsemitted from said electrode provides a majority of said current.
 2. Themethod of claim 1, wherein said measuring a current through saidelectrode comprises measuring a current through a resistor.
 3. Themethod of claim 2, wherein said resistor is located outside of a beam ofsaid radiotherapy radiation.
 4. The method of claim 2, wherein saidresistor is configured to remove heat from said electrode.
 5. The methodof claim 1, wherein said electrode comprises a foil.
 6. The method ofclaim 5, wherein said foil comprises aluminum.
 7. The method of claim 1,further comprising: a scattering foil separate from said electrode.
 8. Amethod of monitoring a radiation dose, the method comprising: couplingan electrode of a scattering/measuring electrode to a voltage measuringcircuit; impinging said electrode by radiation; measuring a voltageacross said resistor corresponding to a radiation dose rate, whereinsaid method is operable in a first mode or a second mode, wherein saidfirst mode corresponds to a radiation dose rate characteristic of FLASHradiotherapy, and wherein said second mode corresponds to a radiationdose rate of less than 40 Gy/s.
 9. The method of claim 8, wherein saidelectrode comprises a foil.
 10. The method of claim 9, wherein said foilis less than 0.001 inches thick.
 11. The method of claim 9, wherein saidfoil comprises brass.
 12. The method of claim 8, wherein said resistoris not impinged by said radiation.
 13. The method of claim 8, whereinsaid resistor is configured to remove heat from said electrode.
 14. Themethod of claim 8, further comprising: a scattering foil separate fromsaid electrode.
 15. A method of controlling a radiation dose in aradiation system, the method comprising: coupling an electrode of ascattering-measuring electrode to a current measuring circuit; exposingthe electrode to radiation; measuring a current through the electrodedue to secondary electron emission from the electrode to indicate a doserate of the radiation; and controlling said radiation system to achievea desired dose rate.
 16. The method of claim 15 wherein said radiationsystem further comprises: a first resistor configured to couple saidelectrode to ground; a first voltage sensor configured to measure afirst voltage across said first resistor; a second electrode in a planeof said first electrode; a second resistor configured to couple saidsecond electrode to ground; a second voltage sensor configured tomeasure a second voltage across said second resistor, wherein saidsecond voltage is indicative of a second radiation dose passing throughsecond first electrode, and wherein a difference between said first andsecond voltages indicates a symmetry error of a radiotherapy beam. 17.The method of claim 16, wherein said electrode comprises a foil.
 18. Themethod of claim 15, wherein a radiotherapy beam is configured to passthrough a collimator prior to impinging said first electrode.
 19. Themethod of claim 15, wherein said first radiation does compriseselectrons.
 20. The method of claim 15, wherein said first electrode isconfigured to scatter a radiotherapy beam.